The present disclosure relates generally to pre-polymer formulations for liquid crystal displays and methods of making bistable electro-optical devices using these pre-polymer formulations.
Polymer dispersed liquid crystal (PDLC) and polymer stabilized liquid crystal (PSLC) technologies have received much attention because of their potential utility for display applications. Adequate control of the phase separation between the liquid crystal and the polymer is important to many commercial applications.
The polymerization of a liquid crystal/monomer at a temperature at which the liquid crystal and monomer are soluble but the liquid crystal/polymer is insoluble is described as polymerization induced phase separation (PIPS). The size of the formed liquid crystal phase is apparently controlled by polymerization kinetics.
Devices of PDLC films sandwiched between transparent electrodes can be switched from a weakly scattering focal conic state to a reflective planar state upon applying an electric field (E) to the electrodes. Both of these states are stable at E=0. This means that the textures are “locked in” and will remain intact until acted upon again (i.e., the device is bistable). Switching from planar to focal conic states requires a low voltage pulse while the return from focal conic to planar requires a higher voltage pulse to drive the device into a homeotropic state which then relaxes to the final planar state.